The coronary arteriovenous fistula (CAVF) is an abnormal communication between one or more coronary arteries and a cardiac chamber or a major venous vessel, allowing direct passage of high-pressure arterial blood into a low-pressure compartment, bypassing the normal myocardial capillary bed. This condition alters cardiac hemodynamics, potentially leading to ischemia, heart failure, and, if left untreated, serious complications such as endocarditis or rupture of the fistula itself.
Coronary arteriovenous fistula is a rare anomaly, found in 0.1-0.2% of patients undergoing coronary angiography, but it can be clinically significant depending on the caliber of the fistula and the amount of blood shunt.
Most CAVFs are congenital, although acquired forms secondary to invasive procedures, thoracic trauma, or complications of endovascular infections also exist.
Early recognition and appropriate management are crucial to prevent progressive hemodynamic deterioration and potentially life-threatening complications associated with this condition.
The coronary arteriovenous fistula is an abnormal communication between a coronary artery and a low-pressure structure, such as a cardiac chamber or venous vessel, allowing the direct passage of high-pressure blood. This condition may have a congenital or acquired origin.
Definite etiological causes primarily include congenital abnormalities in the development of the cardiac vascular system. During embryogenesis, incomplete regression of primitive vascular plexuses may result in persistent abnormal connections between coronary arteries and cardiac chambers or major venous vessels. Acquired forms result from direct vascular wall injuries, such as those caused by penetrating or blunt thoracic trauma, invasive cardiac procedures (catheterizations, transcatheter ablations, pacemaker or defibrillator implants), or severe infections like bacterial endocarditis, leading to erosion and rupture of coronary vascular structures.
Besides these direct causes, some preventable risk factors—though not strictly etiological—can increase the likelihood of developing an acquired CAVF. These include frequent exposure to invasive cardiology procedures, suboptimal management of endovascular infections, and lack of preventive measures against major chest trauma, such as use of seat belts or sports protective gear.
From a pathogenetic perspective, the presence of a communication between a coronary artery and a low-pressure compartment results in a continuous abnormal flow throughout the cardiac cycle. This flow bypasses oxygenated blood away from the myocardial capillary bed, reducing distal myocardial perfusion and leading to the so-called coronary steal phenomenon. Blood intended to supply the myocardium is diverted to a low-resistance chamber, causing ischemia, particularly during exertion when oxygen demand increases.
The resulting pathophysiology is characterized by progressive dilation of the receiving chamber, with the development of volume overload and subsequent congestive heart failure. Additionally, the proximal coronary artery segment, subjected to high and turbulent flow, may undergo aneurysmal dilation, with risk of thrombosis, embolism, or spontaneous rupture. Dilation of cardiac chambers and chronic ischemia further contribute to the development of atrial and ventricular arrhythmias, which worsen the clinical picture.
The clinical manifestations of a coronary arteriovenous fistula depend on several factors, including the size of the fistula, the amount of blood shunted, and the presence of secondary complications. Many small fistulas remain asymptomatic for long periods and are incidentally diagnosed during cardiac examinations performed for other reasons.
Medical history should investigate predisposing factors such as prior thoracic trauma, invasive cardiac interventions, or endocardial infections, as well as symptoms suggestive of myocardial ischemia or heart failure. In adult patients, especially athletes or those engaged in intense physical activities, the presence of progressive symptoms may suggest a significant-sized fistula.
The most common symptoms include:
During physical examination, the most relevant clinical findings are often:
It is important to note that the intensity of the murmur and clinical signs do not always correlate with the anatomical severity of the fistula. Some large-caliber fistulas may present with mild or insidious symptoms, requiring a high degree of clinical suspicion for early recognition.
The diagnosis of a coronary arteriovenous fistula is based on the integration of clinical history, physical findings, and instrumental investigations. In clinical practice, suspicion arises in the presence of a continuous chest murmur or atypical cardiac symptoms not explained by more common conditions.
The first diagnostic step is transthoracic echocardiography (TTE), which, especially when integrated with color Doppler, can detect abnormal flows within the cardiac chambers. In patients with suboptimal acoustic windows or in complex cases, transesophageal echocardiography (TEE) provides more detailed imaging, improving diagnostic sensitivity.
Once an abnormal communication is suspected, coronary angiography remains the gold standard for confirmation. It allows direct visualization of the fistula’s course, the origin and drainage points, and the assessment of shunt flow. Coronary angiography is also fundamental for planning either surgical or percutaneous treatment.
Alternatively, in patients for whom a non-invasive approach is preferred, or when vascular anatomy is complex, cardiac computed tomography (multislice coronary CT) represents a valid diagnostic option. It provides three-dimensional reconstruction of the coronary system and the fistula, offering detailed information on anatomical relationships with surrounding cardiac structures.
Cardiac magnetic resonance imaging (MRI) may be used as a complementary test to evaluate the hemodynamic impact of the fistula, assess ventricular function, and detect signs of secondary myocardial ischemia.
Electrocardiogram (ECG) may reveal ischemia-like abnormalities, such as ST-segment depression or T-wave inversion, or signs of chamber overload. Although not diagnostic, ECG can strengthen clinical suspicion in symptomatic patients.
Exercise stress testing can help assess the presence of ischemia due to the coronary steal phenomenon when history or ECG suggests effort-related angina. However, its execution must be carefully considered based on the patient's clinical stability.
In patients with advanced symptoms or suspected heart failure, arterial blood gas analysis and cardiac biomarker assays (troponin, BNP) may help define the severity of hemodynamic compromise and guide immediate clinical management.
The management of a coronary arteriovenous fistula depends on variables such as fistula size, shunt volume, the presence of symptoms or complications, and long-term evolution risk. Treatment aims to prevent progression to congestive heart failure, myocardial ischemia, or major vascular complications.
In asymptomatic patients with small fistulas and hemodynamically insignificant shunts, a conservative approach with periodic clinical and instrumental monitoring may be appropriate. However, most clinically significant fistulas require active treatment.
Transcatheter percutaneous closure is the first-line therapeutic option in most cases. Using embolization coils, vascular plugs, or dedicated devices, it is possible to occlude the fistula without open-heart surgery. This technique is preferred for single, anatomically favorable fistulas without associated aneurysms.
Surgical correction is indicated in the presence of:
Surgical intervention consists of direct closure of the abnormal communication, possibly combined with coronary artery bypass grafting if the proximal coronary segment is damaged or dilated. In complex cases, cardiopulmonary bypass may be required.
In emergency situations, such as aneurysm rupture or the development of cardiogenic shock, surgical treatment must be performed urgently.
The prognosis of a coronary arteriovenous fistula is generally favorable if recognized and treated early. Successful closure of the fistula, whether percutaneous or surgical, usually allows recovery of cardiac function and resolution of ischemic or congestive symptoms.
The risk of recurrence is low but not negligible, necessitating long-term clinical and instrumental follow-up with serial echocardiography and, in more complex cases, repeated angiographic studies.
In untreated or unrecognized fistulas, there is a significantly increased risk of progression to chronic heart failure, severe ischemia, malignant arrhythmias, or vascular complications (thrombosis, embolism, aneurysmal rupture), with reduced medium- and long-term survival.
Timely and appropriate treatment significantly improves clinical outcomes, reduces morbidity, and allows most patients to return to a normal life without major functional limitations.
Without adequate treatment, a coronary arteriovenous fistula can evolve into a series of potentially serious complications due to persistent hemodynamic alteration and progressive structural damage to the cardiac chambers and coronary arteries.
The most frequent complication is the development of congestive heart failure, resulting from chronic volume overload of the receiving chambers. The abnormal flow through the fistula leads to progressive dilation of the atria and ventricles, with impairment of systolic and diastolic function and signs of systemic and pulmonary congestion.
Reduction in distal myocardial perfusion, due to the coronary steal phenomenon, also exposes patients to the risk of chronic myocardial ischemia. In severe cases, this may promote unstable angina or myocardial infarction, increasing cardiovascular morbidity and mortality.
Another significant risk is the formation of aneurysms in the coronary artery segment proximal to the fistula. Chronic exposure to high and turbulent flow progressively weakens the arterial wall, predisposing to aneurysmal dilation. These aneurysms, besides being sites of potential thrombosis or systemic embolism, may undergo spontaneous rupture, a rare but often fatal event leading to acute hemopericardium and cardiac tamponade.
Structural and functional alterations induced by the fistula also favor the onset of atrial and ventricular arrhythmias. Chamber dilation and chronic ischemia contribute to myocardial electrical instability, increasing the risk of atrial fibrillation, ventricular tachycardias, and, in extreme cases, sudden cardiac arrest.
Finally, the presence of abnormal flow patterns can facilitate bacterial colonization and the formation of vegetations, increasing the risk of infective endocarditis, a complication that can further aggravate the hemodynamic picture and require urgent therapeutic interventions.
Awareness and careful monitoring of potential complications are essential for setting an appropriate therapeutic strategy and improving the long-term prognosis of patients with coronary arteriovenous fistula.